Entity Resolution is the task of identifying which records in a database refer to the same entity. A challenge for builders of databases whose information is culled from multiple sources is the detection of duplicates, where a single real-world entity gives rise to multiple records. Online citation indexes need to be able to navigate through the different capitalization and abbreviation conventions that appear in bibliographic entries. Government agencies need to know whether a record for “Robert Smith” living on “Northwest First Street” refers to the same person as one for a “Bob Smith” living on “1st St. NW”.